Misc: Everything Else Air Fuel Gauge 02 Sensor Lambda Sensor

Cyborg

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So just maybe the LED's around the perimeter of my gauge might come in handy after all. In any event, I can add the analog meter and have a choice of 3 and see which works best as far as visual perception goes.... assuming thats the correct term.
 
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Cyborg

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So when in doubt, read the instructions.... I went back and had another look at them and the LEDs make more sense now. It would have become more obvious once the gauge was powered up... but anyway.. there are a total of 20 LEDs. 6 are red indicating an AFR between 20.00 to 17.93 15 are yellow indicating 17.92 to 12.98 and 9 green indicating 12.97-10.
 

Magnetoman

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So what kind of AFR range (?) are you looking for??
If exactly the right amount of fuel and air had been mixed in the carburetor (i.e. a stoichiometric mix) and combustion was complete there would be no free oxygen left. With the canonical "gasoline" of yore an AFR of 14.7:1 was stochiometric. However, with pure ethanol it is 9:1, and for in-between mixes the AFR is in-between (e.g. 13.8:1 for 15% ethanol). This would seem to be a problem for using our wideband gauges. But, it's not.

A sensor detects the amount of free oxygen that comes out of the combustion chamber, not the AFR. of whatever goes in. If there is no free oxygen left after combustion that condition is λ=1.00 irrespective of the fuel used. If there is excess oxygen (i.e. the mixture fed to the engine was lean) λ will be greater than 1.0 and if there is unburned fuel (rich) λ will be less than 1.0. Most engines provide maximum power for λ in the range of approximately 0.82-0.88.

For the convenience of people who don't like Greek letters most/many/all of these wideband sensors will multiply λ by 14.7 and display the resulting "AFR" instead of, or along with, λ. For gasoline with fairly low ethanol content the desired range would be ~12-13:1. However, the calculated "AFR" is never anything other than an approximation.

So, to answer Robert's question, you shouldn't be looking for any AFR range at all. You should be looking for a λ range, because λ measures the actual product of the combustion irrespective of the composition of the fuel.
 
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Robert Watson

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With the innovate "sniffer" I asked the Chevy LS hot rod guys next door to me, who of course tune by computer with specific LS programs. They have one guy who is an absolute whiz (and well over the age of 50!) and he reckoned that if we got too close to 12.7 on an air cooled (and fuel cooled) motor we would be asking for trouble for street use. On the first bike we did, a Comet, we were well in the 20's all over to start. We started on the pilot, then the cutaway and finally on the main and got the numbers in the 14-17 range. Gas mileage improved from somewhere very dismal to up over 50 mpg so thought we should leave it there.
Before all this techie stuff I would get a nice tick over idle and then start looking to get mileage in the 50 - 55 range on a nice 65-70 mph 100 mile potter on the local highway.
 

Cyborg

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So what kind of AFR range (?) are you looking for??

Good question, but while I was writing this, Magnetoman replied and saved me.
I was figuring with stoich being 14.7 I would want to be on the fat and happy side of that, with an old school hemi (air cooled) combustion chamber.
 

Cyborg

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That video in post 11 deals with different fuels and says to just forget what is in the tank and still use 14.7
 

bmetcalf

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Gas mileage improved from somewhere very dismal to up over 50 mpg so thought we should leave it there.
Before all this techie stuff I would get a nice tick over idle and then start looking to get mileage in the 50 - 55 range on a nice 65-70 mph 100 mile potter on the local highway.

I assume you mean miles per Imperial gallon, not those undersized US ones?
 

Magnetoman

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start looking to get mileage in the 50 - 55 range on a nice 65-70 mph 100 mile potter on the local highway.
For what it's worth, with the pre-Monobloc carburetor on my 1928 Ariel whose only tuning consisted of polishing the needle on the float so fuel wouldn't leak out of holes on the bottom of the carburetor body, the best mileage I got on the Cannonball was 79.2 miles per U.S. gallon (99 miles per Brexit gallon). Second best was 75.2, and worst were 51.4 and 49.4 mpg, the latter riding into stiff headwinds. I had geared the bike high and kept to a pretty steady 50 mph average.

I started out using the highest octane fuel I could find just to be safe, but in Iowa I was confronted with a pump that had a selection of about a half-dozen ethanol mixes, none with an octane rating listed, plus "normal" 87 octane. I used the 87 and then stuck with it for the rest of the Cannonball because it seemed to be fine.

That video in post 11 deals with different fuels and says to just forget what is in the tank and still use 14.7
That advice is completely wrong for the reasons I gave in my previous post.
 
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